JP6395881B2 - Optical scanning device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an optical scanning apparatus that scans each scanning object with a plurality of light beams, and an image forming apparatus including the optical scanning apparatus.

  For example, in an electrophotographic color image forming apparatus, the surface of each photoconductor corresponding to a plurality of colors is uniformly charged, and then the surface of each photoconductor is scanned with each light beam. Form an electrostatic latent image, develop the electrostatic latent image on the surface of each photoconductor with each color toner, form each color toner image on the surface of each photoconductor, and transfer each color toner image from each photoconductor to the intermediate transfer A color toner image is formed on the intermediate transfer body by superimposing and transferring the image on the body, and the color toner image is transferred from the intermediate transfer body to the recording paper.

  The surface of each photoconductor is scanned with each light beam by an optical scanning device. Generally, four color toners of black, cyan, magenta, and yellow are used. Therefore, it is necessary to scan the surface of the four photosensitive members with at least four light beams, and the four light beams are emitted. Four light emitting elements are required.

  In recent years, the image forming apparatus is required to be reduced in size and thickness, and the optical scanning device is required to be reduced in size and thickness. For this reason, the polygon mirror is arranged in the approximate center of the optical scanning device, the two optical systems are arranged symmetrically around the polygon mirror, and the respective light beams emitted from the respective light emitting elements are reflected by the polygon mirror. In each optical system, each light beam is reflected by a plurality of reflecting mirrors and is incident on each photosensitive member.

  For example, Patent Documents 1 and 2 describe such an optical scanning device, in which each light beam is reflected by a plurality of reflecting mirrors and is incident on each photoconductor. The number of reflection mirrors is different for each optical path from the polygon mirror to each photoconductor, and one reflection mirror is provided in the optical path from the polygon mirror to the black photoconductor, and from the polygon mirror to the cyan photoconductor. Two reflecting mirrors are provided in the optical path to the body, three reflecting mirrors are provided in the optical path from the polygon mirror to the magenta photosensitive member, and the optical path from the polygon mirror to the yellow photosensitive member is provided in the optical path. Two reflecting mirrors are provided.

JP 2006-323279 A JP 2010-262245 A

  By the way, the reflectance of the reflection mirror is less than 100%, and a reflection loss occurs. Therefore, the intensity of the light beam decreases as the number of reflections of the light beam by the reflection mirror increases. For this reason, if the number of reflection mirrors provided in the optical path from the polygon mirror to the photoconductor is different for each color of black, cyan, magenta, and yellow as in Patent Documents 1 and 2, the light enters the photoconductor of each color. Large variations occur in the intensity of each light beam. For example, when the reflectivity of the reflection mirror is 90%, the intensity of the light beam of the light emitting element is reduced to 90% in the optical path provided with one reflection mirror, and three reflection mirrors are provided. In the optical path, the intensity of the light beam of the light emitting element is reduced to 73%, and the difference in intensity of the light beam is 17%. This makes it difficult to adjust the intensity of each light beam to match each other.

  In both Patent Documents 1 and 2, the light beam of each light-emitting element is incident on the polygon mirror through one half mirror. For this half mirror, not only the reflectance but also its transmittance affects the intensity of the light beam, so it is not included in the number of reflecting mirrors, but is considered to have an effect equal to or greater than that of the reflecting mirror.

  Therefore, the present invention has been made in view of the above-mentioned conventional problems, and due to the reflection loss of the reflecting mirror, there is a great variation in the intensity of each light beam incident on the photosensitive member of each color. It is an object of the present invention to provide a non-optical scanning device and an image forming apparatus including the same.

In order to solve the above problems, an optical scanning device and an image forming apparatus according to the following first and second aspects are provided.
(1) Optical Scanning Device According to the First Aspect The optical scanning device according to the first aspect of the present invention includes a plurality of light emitting elements, a deflecting unit that deflects a light beam, and the light beam of each light emitting element to the deflecting unit. And an optical system that forms a plurality of optical paths that guide the light beams of the light emitting elements deflected by the deflecting unit to a plurality of scanned objects, respectively, Both are provided with a reflecting mirror that reflects the light beam, and the optical system receives the light beams of the two light emitting elements when viewed from the rotation axis direction of the deflecting unit. The light beam is guided to the deflection unit so as to overlap each other on the same straight line in the rotation axis direction, and one of the two light beams is reflected by the reflection mirror and guided to the deflection unit, and the other Light beam from the reflecting mirror to the deflection unit On the optical path between the reflection mirror and the deflection unit, which is guided to the deflection unit through the position separated in the rotation axis direction and guides the one light beam to the deflection unit in the optical system, and the other A single cylindrical lens that passes the light beams of the two light emitting elements is disposed on an optical path between the light emitting element that emits the light beam and the deflection unit, and the reflection mirror includes: It is supported by a support portion provided in the housing, and a space formed by the reflection mirror, the support portion, and the housing is formed below the reflection mirror, and the other light beam is Pass through the space .
(2) Optical Scanning Device According to Second Embodiment An optical scanning device according to the second aspect of the present invention includes a plurality of light emitting elements, a deflecting unit that deflects a light beam, and the light beam of each light emitting element to the deflecting unit. And an optical system that forms a plurality of optical paths that guide the light beams of the light emitting elements deflected by the deflecting unit to a plurality of scanned objects, respectively, Each includes a reflecting mirror that reflects a light beam, and includes a bottom plate and a casing having a plurality of side plates surrounding the bottom plate, and a single substrate on which the light emitting elements are mounted on one plane, and the optical When the light beams of the two light emitting elements are viewed from the direction of the rotation axis of the deflection unit, the light beams of the two light emitting elements overlap with each other on the same straight line in the direction of the rotation axis. One of the two light beams. A light beam is reflected by the reflecting mirror and guided to the deflecting unit, and the other light beam is guided to the deflecting unit through a position separated from the reflecting mirror in the rotation axis direction of the deflecting unit, The optical system guides light beams of two light emitting elements to an incident spot of the deflecting unit, and the light emitting elements are arranged on the plane of the substrate, so that the light beams are emitted from the light emitting elements. Is orthogonal to the plane, and on the plane, each light emitting element is disposed on two lines in a direction orthogonal to the rotation axis of the deflection unit, and on two lines in the rotation axis direction of the deflection unit. The substrate on which the light emitting elements are mounted is fixed to the outside of one side plate of the plurality of side plates of the housing, and the side plate is attached to each of the light emitting elements. A corresponding through-hole is formed Each light-emitting element, respectively, wherein and faces one of the inside of the housing through the formed said through holes in the side plate, the reflecting mirror is supported by a supporting portion provided in the housing, said reflector A space formed by the reflecting mirror, the support portion, and the housing is formed below the mirror, and the other light beam passes through the space .

  In the present invention configured as described above in the first aspect and the second aspect, each of the optical paths is provided with a reflecting mirror that reflects the light beam, and the number of reflecting mirrors in each optical path is made equal to each other. For this reason, the reflection loss of the reflecting mirror is equal in each of the optical paths, and the intensities of the respective light beams guided to the respective scan objects through the respective optical paths are equal.

Moreover, pre-Symbol light science system, the light beam of the two light emitting elements, the light beam of the two light-emitting element when viewed from a direction of a rotation axis of the deflection unit overlap each other on the same straight line in the direction of the rotation axis The one of the two light beams is reflected by the reflecting mirror and guided to the deflecting unit, and the other light beam is transmitted from the reflecting mirror to the deflecting unit. It passes through a position spaced apart in the rotation axis direction of the deflection unit and is guided to the deflection unit.

Thus, in the optical science system, the light beam of the two light emitting elements, so that the light beam of the two light-emitting element when viewed from the rotational axis of the deflecting portion overlap each other on the same straight line in the direction of the rotation axis Since the light is guided to the deflecting unit, the size of the deflecting unit on which these light beams are incident can be reduced, and the optical scanning device can be downsized. Also, since one of the two light beams is reflected by the reflecting mirror and the other passes through a position separated from the reflecting mirror in the direction of the rotation axis of the deflecting unit, the number of times each of the two light beams is reflected by the reflecting mirror is determined. Can be adjusted.
Furthermore, in the optical scanning device according to the second aspect of the present invention, since each light emitting element is arranged on the plane of the substrate, each light emitting element can be mounted on the same substrate, and the number of components is reduced. be able to. Further, the light emitting elements are arranged on two lines in the transverse direction, since the disposed respectively each of the light-emitting element in the longitudinal direction on the two lines, it is possible to mainly narrow longitudinal pitch, light It is possible to reduce the size of the scanning device.

  Moreover, in the optical scanning device of the first aspect and the second aspect according to the present invention, an empty space through which the other of the two light beams passes between the reflection mirror and the inner surface of the housing of the optical scanning device. Is provided.

  By providing such an empty space, it becomes possible to pass the light beam to a position away from the reflecting mirror.

In the optical scanning device of the first embodiment according to the present invention, prior Symbol optical science system, the light beam of the two light emitting elements leading to inlet morphism spot of the deflection unit, each light emitting element is the same plane is disposed above the perpendicular to the light beam emitting direction to the plane of each light-emitting element, on the plane, the respective light emitting elements, the two lines on the direction orthogonal to the rotation axis of the deflection unit distribution is set, and are disposed respectively in two lines on the rotational axis of the deflection unit.

  Thus, since each light emitting element is arrange | positioned on the same plane, each light emitting element can be mounted on the same board | substrate, and a number of parts can be reduced.

Further, the light emitting elements are arranged on two lines in the transverse direction, since the disposed respectively each of the light-emitting element in the longitudinal direction on the two lines, it is possible to mainly narrow longitudinal pitch, light It is possible to reduce the size of the scanning device.
In the optical scanning devices according to the first and second aspects of the present invention, for example, each of the light emitting elements is arranged on a straight line inclined with respect to the rotation axis direction of the deflection unit on the plane.

  Next, an image forming apparatus according to the present invention includes the optical scanning device according to the first aspect or the second aspect according to the present invention, and forms a latent image on a scanned body by the optical scanning apparatus, and the scanned body. The upper latent image is developed into a visible image, and the visible image is transferred from the scanned body to a sheet.

  Even in such an image forming apparatus, the same effects as those of the optical scanning apparatus of the present invention can be obtained.

  In the present invention, each of the optical paths is provided with a reflecting mirror that reflects the light beam, and the number of reflecting mirrors in each optical path is made equal to each other. For this reason, the reflection loss of the reflecting mirror is equal in each of the optical paths, and the intensities of the respective light beams guided to the respective scan objects through the respective optical paths are equal.

1 is a cross-sectional view illustrating an image forming apparatus including an embodiment of an optical scanning device of the present invention. It is a perspective view which shows the inside of the housing | casing of an optical scanning device from diagonally upward, Comprising: The state which removed the upper cover is shown. It is the perspective view which extracts and shows the some optical member of an optical scanning device, and has shown the state seen from the back side of FIG. It is a top view which extracts and shows a plurality of optical members of an optical scanning device. It is a side view which extracts and shows a plurality of optical members of an optical scanning device. It is a top view which expands and shows each reflective mirror of a 1st incident optical system, and a 2nd incident optical system. (A), (b) is a front view which shows four sets of columnar parts, and a front view which shows the state which supported each reflective mirror.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a sectional view showing an image forming apparatus provided with an embodiment of an optical scanning device of the present invention. The image data handled in the image forming apparatus 1 corresponds to a color image using each color of black (K), cyan (C), magenta (M), yellow (Y), or a single color (for example, black). This corresponds to the monochrome image used. Therefore, four each of the developing device 12, the photosensitive drum 13, the drum cleaning device 14, and the charger 15 are provided in order to form four types of toner images corresponding to the respective colors. , Magenta, and yellow are associated with four image stations Pa, Pb, Pc, and Pd.

  In each of the image stations Pa, Pb, Pc, and Pd, after the residual toner on the surface of the photosensitive drum 13 is removed and collected by the drum cleaning device 14, the surface of the photosensitive drum 13 is set to a predetermined potential by the charger 15. It is charged uniformly, the surface of the photosensitive drum 13 is exposed by the optical scanning device 11, an electrostatic latent image is formed on the surface, and the electrostatic latent image on the surface of the photosensitive drum 13 is developed by the developing device 12, A toner image is formed on the surface of the photosensitive drum 13. As a result, a toner image of each color is formed on the surface of each photosensitive drum 13.

  Subsequently, while the intermediate transfer belt 21 is moved in the direction of the arrow C, the residual toner on the intermediate transfer belt 21 is removed and collected by the belt cleaning device 22, and then each color toner image on the surface of each photoconductive drum 13 is intermediate transferred. The toner images are sequentially transferred onto the belt 21 and overlapped to form a color toner image on the intermediate transfer belt 21.

  A nip area is formed between the intermediate transfer belt 21 and the transfer roller 23a of the secondary transfer device 23, and the recording sheet conveyed through the S-shaped sheet conveyance path R1 is sandwiched in the nip area. While being conveyed, the color toner image on the surface of the intermediate transfer belt 21 is transferred onto the recording paper. Then, the recording paper is sandwiched between the heating roller 24 and the pressure roller 25 of the fixing device 17 and heated and pressed to fix the color toner image on the recording paper.

  On the other hand, the recording paper is pulled out from the paper feeding cassette 18 by the pickup roller 33 and is transported through the paper transporting path R 1, via the secondary transfer device 23 and the fixing device 17, and through the paper discharge roller 36. To 39. In this paper transport path R1, after the recording paper is temporarily stopped and the leading edges of the recording paper are aligned, the recording paper is fed in accordance with the transfer timing of the toner image in the nip area between the intermediate transfer belt 21 and the transfer roller 23a. A registration roller 34 that starts conveyance, a conveyance roller 35 that prompts conveyance of the recording paper, a paper discharge roller 36, and the like are arranged.

  Next, the configuration of the optical scanning device 11 of this embodiment will be described in detail with reference to FIGS. FIG. 2 is a perspective view showing the inside of the housing 41 of the optical scanning device 11 of FIG. 1 as viewed obliquely from above, and shows a state where the upper lid is removed. FIG. 3 is a perspective view showing a plurality of optical members extracted from the optical scanning device 11, and shows a state viewed from the back side of FIG. 4 and 5 are a plan view and a side view showing a plurality of optical members extracted from the optical scanning device 11. FIG. FIG. 5 also shows the photosensitive drums 13 arranged outside the optical scanning device 11.

  The housing 41 has a rectangular bottom plate 41a and four side plates 41b and 41c surrounding the bottom plate 41a. A square polygon mirror 42 in a plan view is arranged at the approximate center of the bottom plate 41a. Further, the polygon motor 43 is fixed substantially at the center of the bottom plate 41 a, the center of the polygon mirror 42 is connected and fixed to the rotation axis of the polygon motor 43, and the polygon mirror 42 is rotated by the polygon motor 43.

  In addition, on the outer side of one side plate 41b of the housing 41, a driving substrate 46 on which two first semiconductor lasers 44a and 44b and two second semiconductor lasers 45a and 45b (four semiconductor lasers in total) are mounted. Is fixed. The first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b face the inside of the housing 41 through the respective holes formed in the side plate 41b.

  Assuming a virtual straight line M extending in the main scanning direction X through the center of the polygon mirror 42, the first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b are symmetrical about the virtual straight line M. Is arranged. A direction perpendicular to the main scanning direction X is defined as a sub-scanning direction Y, and a direction perpendicular to the main scanning direction X and the sub-scanning direction Y (longitudinal direction of the rotation axis of the polygon motor 43) is defined as a height direction Z.

  The drive board 46 is a flat printed board and has circuits for driving the first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b. Each of the first semiconductor lasers 44a and 44b and each of the second semiconductor lasers 45a and 45b are arranged on a substantially same plane (YZ plane) by being mounted on a flat printed board, and with respect to the plane, The respective light beams L1 to L4 are emitted in the vertical direction (main scanning direction X) and inward of the housing 41.

  On the drive substrate 46 (YZ plane), the first semiconductor lasers 44a and 44b are arranged at different positions in the sub-scanning direction Y and the height direction Z, and similarly, the second semiconductor lasers 45a and 45b are also in the sub-scanning direction. The first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b are arranged at four corners q1 to q4 of an inverted isosceles trapezoid Q indicated by a one-dot chain line. Has been.

  Here, when the first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b are arranged at the four corners q1 to q4 of the inverted isosceles trapezoid Q, the first semiconductor lasers 44a and 44b and the second semiconductor lasers 44a and 44b Compared with the case where the two semiconductor lasers 45a and 45b are arranged at the four corners of the square, the distance between the first semiconductor lasers 44a and 44b and the distance between the second semiconductor lasers 45a and 45b are kept high. With respect to the vertical direction Z (longitudinal direction), the arrangement space of the first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b can be reduced, and the height of the optical scanning device 11 can be reduced.

  Further, the first incident optical system 51 that guides the light beams L1 and L2 of the first semiconductor lasers 44a and 44b to the polygon mirror 42, and the light beams L3 and L4 of the second semiconductor lasers 45a and 45b to the polygon mirror 42. A second incident optical system 52 is provided. The first incident optical system 51 includes two collimator lenses 53a and 53b, two apertures 54, two reflecting mirrors 55a and 55b arranged at the same height as the first semiconductor laser 44a, a cylindrical lens 56, and the like. Consists of. Similarly, the second incident optical system 52 includes two collimator lenses 57a and 57b, two apertures 58, two reflecting mirrors 59a and 59b arranged at the same height as the second semiconductor laser 45b, and a cylindrical. The lens 56 and the like. Each collimator lens 53a, 53b, each aperture 54, and each reflection mirror 55a, 55b of the first incident optical system 51, each collimator lens 57a, 57b, each aperture 58, and each reflection mirror 59a of the second incident optical system 52. , 59b are arranged symmetrically about the virtual straight line M. The virtual straight line M passes through the center of the cylindrical lens 56, one half of the cylindrical lens 56 divided by the virtual straight line M is disposed in the first incident optical system 51, and the other half of the cylindrical lens 56 is half-sided. Arranged in the second incident optical system 52.

  Further, a first imaging optical system 61 that guides the light beams L1 and L2 of the first semiconductor lasers 44a and 44b reflected by the polygon mirror 42 to the two photosensitive drums 13 for black and cyan, and a polygon mirror A second imaging optical system 62 is provided that guides the light beams L3 and L4 of the second semiconductor lasers 45a and 45b reflected by 42 to the two photosensitive drums 13 for magenta and yellow. The first imaging optical system 61 includes an fθ lens 63 and four reflecting mirrors 64a, 64b, 64c, 64d, and the like. Similarly, the second imaging optical system 62 includes an fθ lens 65 and four reflecting mirrors 66a, 66b, 66c, 66d, and the like. The fθ lens 63 and the reflection mirrors 64a, 64b, 64c, and 64d of the first imaging optical system 61, and the fθ lens 65 and the reflection mirrors 66a, 66b, 66c, and 66d of the second imaging optical system 62 are virtual. They are arranged symmetrically about the straight line M.

  A substrate 73 on which the BD mirror 71 and the BD sensor 72 are mounted is provided on the first imaging optical system 61 side, and a substrate 76 on which the BD mirror 74 and the BD sensor 75 are mounted is also provided on the second imaging optical system 62 side. ing. The BD mirror 71 and the BD sensor 72 on the first imaging optical system 61 side and the BD mirror 74 and the BD sensor 75 on the second imaging optical system 62 side are arranged symmetrically about the virtual straight line M. .

  Next, the optical paths until the light beams L1 and L2 of the first semiconductor lasers 44a and 44b enter the respective photosensitive drums 13 and the light beams L3 and L4 of the second semiconductor lasers 45a and 45b are respectively Each optical path until it enters the photosensitive drum 13 will be described.

  The light beam L1 of the first semiconductor laser 44a is transmitted through the collimator lens 53a to be collimated, is focused by the aperture 54, is incident on the reflecting mirrors 55a and 55b, is reflected, and passes through the cylindrical lens 56. The light enters the reflecting surface 42 a of the polygon mirror 42. In addition, the light beam L2 of the first semiconductor laser 44b is transmitted through the collimator lens 53b to be collimated, and is narrowed down by the aperture 54 to pass through the empty space E below the reflecting mirror 55b (downward in the height direction Z). Passes through the cylindrical lens 56 and enters the reflecting surface 42 a of the polygon mirror 42. The cylindrical lens 56 condenses and emits the light beams L1 and L2 so that the light beams L1 and L2 are substantially converged by the reflecting surface 42a of the polygon mirror 42 only in the height direction Z.

  Here, although the first semiconductor lasers 44a and 44b are arranged at different positions in the sub-scanning direction Y on the drive substrate 46 (YZ plane), the light beam L1 of the first semiconductor laser 44a is reflected by each reflection mirror. Reflected by 55a and 55b and displaced in the sub-scanning direction Y to the first optical path overlapping region J1. The first optical path overlapping region J1 is a region including the optical paths of the light beams L1 and L2 from the reflecting mirror 55b to the reflecting surface 42a of the polygon mirror 42 through the cylindrical lens 56. In the first optical path overlap region J1, the light beams L1 and L2 overlap each other and pass through the same straight line when viewed in plan (as viewed in the rotation axis direction of the polygon mirror 42) as shown in FIG. . That is, the light beams L1 and L2 overlap in the height direction Z.

  Further, although the first semiconductor lasers 44a and 44b are arranged at different positions in the height direction Z on the drive substrate 46 (YZ plane), the light beams L1 and L2 of the first semiconductor lasers 44a and 44b The incident spots (first incident spots) of the light beams L1 and L2 are substantially overlapped on the reflecting surface 42a of the polygon mirror 42 by setting the emission direction or the direction of the reflecting mirrors 55a and 55b. For this reason, in the first optical path overlapping region J1, the light beams L1 and L2 of the first semiconductor lasers 44a and 44b are incident on the reflecting surface 42a of the polygon mirror 42 from diagonally upward and diagonally downward directions. Then, when the light beams L1 and L2 are reflected by the reflection surface 42a of the polygon mirror 42, they are separated from each other in the diagonally downward direction and the diagonally upward direction. One light beam L1 is reflected obliquely downward by the reflection surface 42a of the polygon mirror 42, passes through the fθ lens 63 and is reflected by one reflection mirror 64a, and forms a black toner image. Is incident on. The other light beam L2 is reflected obliquely upward by the reflecting surface 42a of the polygon mirror 42, passes through the fθ lens 63, and is sequentially reflected by the three reflecting mirrors 64b, 64c, and 64d. The light enters the photosensitive drum 13 to be formed.

  Further, the polygon mirror 42 is rotated at a constant angular velocity by a polygon motor 43, sequentially reflects each light beam L1, L2 on each reflecting surface 42a, and repeats each light beam L1, L2 in the main scanning direction X at a constant angular velocity. To deflect. The fθ lens 63 condenses and emits the light beams L1 and L2 so as to have a predetermined beam diameter on the surface of each photosensitive drum 13 in both the main scanning direction X and the sub-scanning direction Y, and The light beams L1 and L2 deflected at a constant angular velocity in the main scanning direction X by the polygon mirror 42 are converted so as to move at a constant linear velocity along the main scanning lines on the respective photosensitive drums 13. Thus, the light beams L1 and L2 repeatedly scan the surface of the photosensitive drum 13 in the main scanning direction X.

  One light beam L1 is reflected by the BD mirror 71 and enters the BD sensor 72 immediately before the main scanning of each photosensitive drum 13 by the light beams L1 and L2 is started. The BD sensor 72 receives the light beam L1 at a timing immediately before the main scanning of each photosensitive drum 13 is started, and outputs a BD signal indicating the timing immediately before the start of the main scanning. The start timing of main scanning of each photosensitive drum 13 on which black and cyan toner images are formed is set in accordance with the BD signal, and the light beams L1 and L2 are modulated in accordance with the black and cyan image data. Be started.

  On the other hand, the photosensitive drums 13 on which the black and cyan toner images are formed are driven to rotate, and the two-dimensional surface (circumferential surface) of each photosensitive drum 13 is scanned by the light beams L1 and L2. Each electrostatic latent image is formed on the surface of each photosensitive drum 13.

  Next, the light beam L3 of the second semiconductor laser 45a is transmitted through the collimator lens 57a to be collimated, is narrowed down by the aperture 58, and is vacant space E below the reflection mirror 59a (downward in the height direction Z). , Passes through the cylindrical lens 56, and enters the reflecting surface 42 a of the polygon mirror 42. In addition, the light beam L4 of the second semiconductor laser 45b is transmitted through the collimator lens 57b to be collimated, is focused by the aperture 58, is incident on the reflection mirrors 59a and 59b, is reflected, and is transmitted through the cylindrical lens 56. Then, the light enters the reflecting surface 42a of the polygon mirror 42.

  Although the second semiconductor lasers 45a and 45b are arranged at different positions in the sub-scanning direction Y on the drive substrate 46 (YZ plane), the light beam L4 of the second semiconductor laser 45b is reflected by the reflection mirrors 59a and 59b. And is displaced in the sub-scanning direction Y to the second optical path overlap region J2. The second optical path overlapping region J2 is a region including the optical paths of the light beams L3 and L4 from the reflecting mirror 59a through the cylindrical lens 56 to the reflecting surface 42a of the polygon mirror 42. In the second optical path overlap region J2, the light beams L3 and L4 overlap each other and pass through the same straight line when viewed in plan (as viewed in the rotation axis direction of the polygon mirror 42) as shown in FIG. . That is, the light beams L3 and L4 overlap in the height direction Z.

  In addition, although the second semiconductor lasers 45a and 45b are arranged at different positions in the height direction Z on the drive substrate 46 (YZ plane), the light beams L3 and L4 of the second semiconductor lasers 45a and 45b The incident spots (second incident spots) of the light beams L3 and L4 are substantially overlapped on the reflecting surface 42a of the polygon mirror 42 by setting the emission direction or the direction of the reflecting mirrors 59a and 59b. For this reason, in the second optical path overlapping region J2, the light beams L3 and L4 of the second semiconductor lasers 45a and 45b are incident on the reflecting surface 42a of the polygon mirror 42 from obliquely downward and obliquely upward directions. Then, when the light beams L3 and L4 are reflected by the reflecting surface 42a of the polygon mirror 42, they are separated from each other in the diagonally upward direction and the diagonally downward direction. One light beam L3 is reflected obliquely upward by the reflecting surface 42a of the polygon mirror 42, passes through the fθ lens 65, and is sequentially reflected by the three reflecting mirrors 66b, 66c, and 66d to form a magenta toner image. Is incident on the photosensitive drum 13. The other light beam L4 is reflected obliquely downward by the reflecting surface 42a of the polygon mirror 42, passes through the fθ lens 65 and is reflected by one reflecting mirror 66a, and forms a yellow toner image. Incident on the body drum 13.

  The other light beam L4 is reflected by the BD mirror 74 and incident on the BD sensor 75 immediately before the main scanning of each photosensitive drum 13 by the light beams L3 and L4 is started. A BD signal indicating the timing immediately before the start of main scanning of each photosensitive drum 13 by each of the light beams L3 and L4 is output, and a magenta and yellow toner image is formed according to this BD signal. The scanning start timing is set, and modulation of the light beams L3 and L4 corresponding to the magenta and yellow image data is started.

  On the other hand, the respective photosensitive drums 13 on which magenta and yellow toner images are formed are driven to rotate, and the two-dimensional surfaces (peripheral surfaces) of the respective photosensitive drums 13 are scanned by the respective light beams L3 and L4. Each electrostatic latent image is formed on the surface of each photosensitive drum 13.

  In the optical scanning device 11 having such a configuration, the polygon mirror 42 is disposed substantially at the center of the bottom plate 41a of the housing 41, and each first semiconductor laser 44a is centered on a virtual straight line M passing through the center of the polygon mirror 42. 44b and the second semiconductor lasers 45a and 45b are arranged symmetrically, the first incident optical system 51 and the second incident optical system 52 are arranged symmetrically, and the first imaging optical system 61 and the second imaging Since the optical system 62 is arranged symmetrically, when viewed from the side, the polygon mirror 42, the first semiconductor lasers 44a and 44b, the second semiconductor lasers 45a and 45b, the first incident optical system 51, and The second incident optical system 52 and the like are concentrated in a small space, and the optical scanning device 11 can be generally downsized.

  Further, the light beams L1 and L2 of the first semiconductor lasers 44a and 44b are made incident on substantially the same first incident spot on the reflecting surface 42a of the polygon mirror 42, and the light beams L3 of the second semiconductor lasers 45a and 45b. , L4 is incident on substantially the same second incident spot on the reflecting surface 42a of the polygon mirror 42, the thickness of the polygon mirror 42 can be reduced, and the polygon mirror 42 can increase the height of the optical scanning device 11. There is no cause to increase the height.

  In addition, the light beam L1 of the first semiconductor laser 44a is displaced in the sub-scanning direction Y to the first optical path overlap region J1 near the virtual straight line M (center of the apparatus) by the reflecting mirrors 55a and 55b, and then enters the polygon mirror 42. And the reflecting mirrors 59a and 59b displace the light beam L4 of the second semiconductor laser 45b to the second optical path overlapping region J2 near the virtual straight line M (center of the apparatus) in the sub-scanning direction Y, and then to the polygon mirror 42. Since it is incident, the diameter of the polygon mirror 42 can be reduced, the first imaging optical system 61 and the second imaging optical system 62 can be brought close to each other, and the lateral width of the optical scanning device 11 can be suppressed. The optical scanning device 11 can be downsized.

  Further, since the first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b are mounted on the same drive substrate 46, the number of parts is reduced, and the semiconductor lasers 44a, 44b, 45a and 45b are reduced. Wiring can be simplified.

  By the way, in accordance with the rotation of the polygon mirror 42, each light beam L <b> 1 to L <b> 4 is moved from the polygon mirror 42 to each photoconductor drum 13 so as to move along the main scanning line on the respective photoconductor drum 13 at the same linear velocity. It is necessary to equalize the optical path lengths of the light beams L1 to L4. For this reason, in the first imaging optical system 61, the light beam L1 is reflected by only one reflecting mirror 64a, the optical path of the light beam L1 is bent only once and set short, and the light beam L2 is set to 3 Reflected by the reflecting mirrors 64b to 64d, the optical path of the light beam L2 is bent three times to extend the optical path of the light beam L2. Similarly, also in the second imaging optical system 62, the light beam L4 is reflected by only one reflecting mirror 66a, the optical path of the light beam L4 is bent once and set short, and three light beams L3 are set. Are reflected by the reflection mirrors 66b to 66d, and the optical path of the light beam L3 is bent three times to extend the optical path of the light beam L3. Thereby, even if the positions of the photosensitive drums 13 with respect to the polygon mirror 42 are different, the optical path lengths of the light beams L1 to L4 are equal to each other.

  However, since each of the light beams L1 and L4 is reflected by only one reflection mirror 64a and 66a, the reflection loss is small and the light intensity is hardly reduced. In contrast, the light beams L2 and L3 are not reflected. Is reflected by the three reflecting mirrors 64b to 64d and 66b to 66d, the reflection loss is large and the light intensity is greatly reduced. If an adjustment is made to make the intensities of the light beams L1 to L4 coincide with each other in a state where the difference in light intensity between the light beams L1 and L4 and the light beams L2 and L3 is large, this adjustment is performed. It becomes difficult.

  Therefore, in the present embodiment, in the first incident optical system 51, the light beam L1 is reflected by the two reflecting mirrors 55a and 55b and then incident on the polygon mirror 42, and the polygon mirror without reflecting the light beam L2 is used. Similarly, in the second incident optical system 52, the light beam L4 is reflected by the two reflecting mirrors 59a and 59b and then incident on the polygon mirror 42, and the light beam L3 is not reflected and is reflected by the polygon mirror. 42 is incident. Therefore, the light beam L1 is reflected three times by the two reflecting mirrors 55a and 55b and the one reflecting mirror 64a, and the light beam L2 is reflected three times by the three reflecting mirrors 64b to 64d. L3 is reflected three times by the three reflecting mirrors 66b to 66d, and the light beam L4 is reflected three times by the two reflecting mirrors 59a and 59b and one reflecting mirror 66a, and thus each of the light beams L1 to L4. Each of these is reflected three times by three reflecting mirrors. As a result, the reflection losses in the optical paths of the light beams L1, L2, L3, and L4 are the same, and the light intensities of the light beams L1 to L4 incident on the photosensitive drums 13 are substantially the same. Adjustment for making the light intensities of L4 coincide with each other becomes easy.

  The optical path length of each of the light beams L1 and L4 is increased by the distance of the reflection mirrors 55a and 55b and the distance of the reflection mirrors 59a and 59b, respectively. The optical path lengths of the light beams L2 and L3 can be increased by the distance between them so that the optical path lengths of the light beams L1 and L4 can be easily made equal.

  Next, the two reflecting mirrors 55a and 55b of the first incident optical system 51 and the two reflecting mirrors 59a and 59b of the second incident optical system 52 will be described in detail.

  FIG. 6 is an enlarged plan view showing the first incident optical system 51 and the second incident optical system 52. As shown in FIG. 6, the bottom plate 41a of the housing 41 is provided with four sets of columnar portions 81a to 81h. The reflection mirror 55a is supported between the columnar portions 81a and 81b, and each columnar portion 81c. 81d, the reflection mirror 55b is supported, the reflection mirror 59a is supported between the columnar portions 81e and 81f, and the reflection mirror 59b is supported between the columnar portions 81g and 81h.

  FIGS. 7A and 7B are a front view showing four sets of columnar portions 81a to 81h and a front view showing a state in which the reflecting mirrors 55a, 55b, 59a, and 59b are supported. As shown in FIGS. 7A and 7B, the opposing surfaces of the columnar portions 81a and 81b, the opposing surfaces of the columnar portions 81c and 81d, the opposing surfaces of the columnar portions 81e and 81f, and the columnar portions 81g and 81h. Grooves 82 are formed on the opposing surfaces of the columnar portions from the tips of the columnar portions to near the center, and both ends of the reflection mirror 55a are inserted and bonded to the grooves 82 of the columnar portions 81a and 81b. Both ends of the reflection mirror 55b are inserted and bonded to the grooves 82 of the portions 81s and 81d, and both ends of the reflection mirror 59a are inserted and bonded to the grooves 82 of the columnar portions 81e and 81f, and the grooves of the columnar portions 81g and 81h. Both ends of the reflection mirror 59b are inserted and bonded to 82.

  Each reflection mirror 55a, 55b, 59a, 59b is supported by four sets of columnar portions 81a-81h so as to be separated from the bottom plate 41a, and between each reflection mirror 55a, 55b, 59a, 59b and the bottom plate 41a, that is, each An empty space E is formed below the reflection mirrors 55a, 55b, 59a, 59b (downward in the height direction Z).

  Here, as described above with reference to FIG. 5, in the drive substrate 46 (YZ plane), the first semiconductor lasers 44 a and 44 b are arranged at different positions in the sub-scanning direction Y and the height direction Z. Similarly, the second semiconductor lasers 45a and 45b are also arranged at mutually different positions in the sub-scanning direction Y and the height direction Z, and the first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b are shown by alternate long and short dash lines. Arranged at four corners q1 to q4 of the inverted isosceles trapezoid Q shown.

  Further, as apparent from FIG. 5, in the first incident optical system 51, the reflecting mirrors 55a and 55b are arranged at the same height as the first semiconductor laser 44a, and an empty space E is provided below the reflecting mirrors 55a and 55b. Is formed. Similarly, in the second incident optical system 52, the reflecting mirrors 59a and 59b are arranged at the same height as the second semiconductor laser 45b, and an empty space E is formed below the reflecting mirrors 59a and 59b.

  As shown in FIG. 6, in the first incident optical system 51, the light beam L1 of the first semiconductor laser 44a is reflected twice by each of the reflection mirrors 55a and 55b and reaches the first optical path overlapping region J1 in the sub-scanning direction. In the first optical path overlap region J1, the light beams L1 and L2 are overlapped in the height direction Z so as to pass through the same straight line. Further, as shown in FIG. 5, the light beam L2 of the first semiconductor laser 44b passes through the empty space E below the reflection mirror 55b. Therefore, the light beam L1 is reflected by the two reflecting mirrors 55a and 55b, and the light beam L2 passes through the empty space E below the reflecting mirror 55b without being reflected.

  Similarly, in the second incident optical system 52, the light beam L4 of the second semiconductor laser 45b is reflected twice by the respective reflection mirrors 59a and 59b and displaced in the sub-scanning direction Y to the second optical path overlapping region J2, In the second optical path overlap region J2, the light beams L3 and L4 are overlapped in the height direction Z so as to pass through the same straight line. Further, as shown in FIG. 5, the light beam L3 of the second semiconductor laser 45a passes through the empty space E below the reflection mirror 59a. Accordingly, the light beam L4 is reflected by the two reflecting mirrors 55a and 55b, and the light beam L3 passes through the empty space E below the reflecting mirror 59a without being reflected.

  That is, in the first incident optical system 51, the light beam L1 is reflected by the two reflecting mirrors 55a and 55b, and the light beam L2 is not reflected. The light is reflected by the reflecting mirrors 59a and 59b, and the light beam L3 is not reflected.

  As described above, in the first and second incident optical systems 51 and 52, the first semiconductor lasers 44a and 44b and the second semiconductor lasers 45a and 45b are arranged at four angles q1 to q4 of the inverted isosceles trapezoid Q, respectively. The first semiconductor laser 44a and the reflection mirrors 55a and 55b are arranged at the same height, and the second semiconductor laser 45b and the reflection mirrors 59a and 59b are arranged at the same height. The light beam L1 of 44a is reflected by the two reflecting mirrors 55a and 55b, the light beam L4 of the second semiconductor laser 45b is reflected by the two reflecting mirrors 59a and 59b, and the light beam L2 of the first semiconductor laser 44a is reflected. The light beam L3 of the second semiconductor laser 45b is not reflected. Thereby, three reflection mirrors are provided in any of the optical paths of the light beams L1, L2, L3, and L4, and the reflection loss of the light beams in these optical paths is set to be the same. For this reason, the light intensities of the light beams L1 to L4 incident on the photoconductor drums 13 are substantially the same, and adjustment for making the light intensities of the light beams L1 to L4 coincide with each other is facilitated.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Optical scanning apparatus 12 Developing apparatus 13 Photosensitive drum (to-be-scanned body)
14 Drum cleaning device 15 Charger 17 Fixing device 21 Intermediate transfer belt 22 Belt cleaning device 23 Secondary transfer device 33 Pickup roller 34 Registration roller 35 Transport roller 36 Paper discharge roller 41 Housing 42 Polygon mirror (deflection unit)
43 Polygon motors 44a, 44b First semiconductor laser (light emitting element)
45a, 45b Second semiconductor laser (light emitting element)
46 drive substrate 51 first incident optical system (first optical system)
52 Second incident optical system (second optical system)
53a, 53b, 57a, 57b Collimator lenses 55a, 55b, 59a, 59b Reflection mirror 56 Cylindrical lens 61 First imaging optical system (first optical system)
62 Second imaging optical system (second optical system)
63, 65 fθ lenses 64a-64d, 66a-66d Reflective mirrors 71, 74 BD mirror 72, 75 BD sensor 73, 76 Substrate 81a-81h Columnar part

Claims (6)

A plurality of light emitting elements, a deflecting unit that deflects a light beam, and a light beam of each light emitting element is guided to the deflecting unit, and the light beam of each light emitting element deflected by the deflecting unit is a plurality of scanned objects. An optical scanning device including an optical system that forms a plurality of optical paths respectively leading to
Each of the optical paths is provided with a reflection mirror that reflects the light beam,
The optical system deflects the light beams of two light emitting elements so that the light beams of the two light emitting elements overlap each other on the same straight line in the rotation axis direction when viewed from the rotation axis direction of the deflection unit. To the department,
Of the two light beams, one light beam is reflected by the reflection mirror and guided to the deflection unit, and the other light beam passes through a position separated from the reflection mirror in the rotation axis direction of the deflection unit. And led to the deflection unit,
In the optical system, on the optical path between the deflection mirror that guides the one light beam to the deflecting unit and on the optical path between the light emitting element that emits the other light beam and the deflecting unit. In addition, a single cylindrical lens that allows the light beams of the two light emitting elements to pass therethrough is disposed,
The reflection mirror is supported by a support portion provided in the housing,
A space formed by the reflection mirror, the support portion, and the housing is formed below the reflection mirror,
The optical scanning device characterized in that the other light beam passes through the space . The optical scanning device according to claim 1,
The optical system guides the light beams of two light emitting elements to the incident spot of the deflection unit,
Each of the light emitting elements is disposed on the same plane, and the light beam emission direction of each of the light emitting elements is orthogonal to the plane, and on the plane, each of the light emitting elements is connected to the rotation axis of the deflection unit. An optical scanning device, which is disposed on two lines in a direction perpendicular to each other and on two lines in the rotation axis direction of the deflecting unit. A plurality of light emitting elements, a deflecting unit that deflects a light beam, and a light beam of each light emitting element is guided to the deflecting unit, and the light beam of each light emitting element deflected by the deflecting unit is a plurality of scanned objects. An optical scanning device including an optical system that forms a plurality of optical paths respectively leading to
Each of the optical paths is provided with a reflection mirror that reflects the light beam,
A housing having a bottom plate and a plurality of side plates surrounding the bottom plate, and a single substrate on which each light emitting element is mounted on one plane,
The optical system deflects the light beams of two light emitting elements so that the light beams of the two light emitting elements overlap each other on the same straight line in the rotation axis direction when viewed from the rotation axis direction of the deflection unit. To the department,
Of the two light beams, one light beam is reflected by the reflection mirror and guided to the deflection unit, and the other light beam passes through a position separated from the reflection mirror in the rotation axis direction of the deflection unit. And led to the deflection unit,
The optical system guides the light beams of two light emitting elements to the incident spot of the deflection unit,
Each of the light emitting elements is disposed on the plane of the substrate, and an emission direction of a light beam of each of the light emitting elements is orthogonal to the plane, and each of the light emitting elements is rotated by the deflection unit. Arranged on two lines in a direction perpendicular to the axis, and arranged on two lines in the direction of the rotation axis of the deflection unit,
The substrate on which each of the light emitting elements is mounted is fixed to the outside of one side plate of the plurality of side plates of the housing,
The side plate has a through hole corresponding to each of the light emitting elements,
Each of the light emitting elements faces the inside of the casing through the through holes formed in the one side plate,
The reflection mirror is supported by a support portion provided in the housing,
A space formed by the reflection mirror, the support portion, and the housing is formed below the reflection mirror,
The optical scanning device characterized in that the other light beam passes through the space . The optical scanning device according to claim 2 or 3, wherein
Each of the light emitting elements is arranged on a straight line inclined with respect to the rotation axis direction of the deflection unit on the plane. An optical scanning device according to any one of claims 1 to 4, wherein
The support portion is a pair of columnar portions, the reflection mirror is supported between the pair of columnar portions, and the space is surrounded by the reflection mirror, the pair of columnar portions, and the housing. An optical scanning device characterized by being an empty space . Includes the optical scanning apparatus according to any one of claims 1 to 5, to form a latent image on the scanned object by the optical scanning apparatus, a visible image of the latent image on the scanning target An image forming apparatus that develops the visible image and transfers the visible image from the scanned body onto a sheet.

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